In a high-rise building or the like, the double deck elevator in which two cages are constructed vertically on two stages have been utilized as traffic means for vertical traffic in the building in order to improve space efficiency of the building. In this kind of the double deck elevator as shown in FIG. 1, a type having an inter-cage distance adjusting mechanism for adjusting the distance between the cages by moving the upper and lower cages 2, 4 within a cage frame 1 to opposite directions by using a crank mechanism 7 has been well known. In the type shown in FIG. 1, the upper cage 2 and the lower cage 4 are installed on the crank mechanism 7 mounted on the central portion of the cage frame 1 and the upper cage 2 and the lower cage 4 are driven to opposite directions by means of a motor 8 and ball screws 9 in a state in which they are balanced by their own weights. In another type, while one of vertically arranged cages is stationary, the other cage is movable so as to adjust the distance between the cages.
Because in the double deck elevator having the inter-cage distance adjusting mechanism, that adjustment operation is carried out during elevator operation, passengers in the cage may feel anxious or discomfort.
Conventionally, as a method for solving such a problem, the one described in Jpn. Pat. Appln. KOKAI Publication No. 2001-302115 has been well known. According to this publication, a cage driving unit is controlled such that at the same time when a destination floor is determined and a winding machine (elevator) begins to decelerate, the inter-cage distance adjusting operation starts and that adjusting operation is completed during elevator deceleration.
FIG. 2 shows an operation pattern of the winding machine and the cage driving unit proposed in the same publication. Here, a double deck elevator in which the upper and lower cages are driven to opposite directions at the same time is assumed. Curve S1 indicates an operation velocity pattern of the winding machine (that is, a velocity change of the cage frame of the elevator), curve S2 indicates the velocity change of one cage driven in the elevator advancement direction, curve S2′ indicates the velocity change of the other cage driven to an opposite direction to the elevator advancement direction and curve S3 indicates an operation velocity pattern of the cage driving unit. The velocity change S2 of one cage is expressed as S1+S3, while the velocity change S2′ of the other cage is expressed as S1−S3.
Usually, the elevator accelerates at a specific acceleration from a startup floor with a driving of the winding machine and then enters a constant velocity operation. After the destination floor is determined, a deceleration operation starts at time t1, a specified deceleration is maintained in an interval between time t2 and time t3 and then, deceleration is lowered from time t3 until time t4 at which the elevator stops with the safety. Then, the elevator stops. The cage driving unit is controlled according to an operation pattern in the elevator deceleration period so as to adjust the distance between the cages.
The reason why the cage adjustment operation is carried out during elevator deceleration is that if it is executed in other period than the deceleration period, no destination floor is determined so that how long the distance between the cages should be secured is not known (the distance being dependent on destination floors) and if the inter-cage distance adjustment is carried out in the period of the elevator constant velocity moving, a velocity change by the adjustment operation is transmitted directly to passengers. If the inter-cage distance adjustment is carried out according to an operation pattern during elevator deceleration as shown in FIG. 2, the upper and lower cages turn into a velocity pattern of constant acceleration, low velocity and constant deceleration, so that passengers in the cage hardly feel a velocity change by the adjustment operation.
However, according to the conventional method in which as described above, the distance between the cages is adjusted in the deceleration period from startup of the elevator deceleration until elevator stop, the velocity change at the time of the adjustment operation is large if the adjustment distance between the cages is large or the elevator deceleration period is short. That is, because the distance between the cages needs to be adjusted corresponding to a destination floor in a short time in the deceleration period, the velocity change between t1 and t2 shown in FIG. 2 is increased and the velocity change provides the passengers with a feeling of disharmony so that they feel discomfort.
Further, a large capacity cage driving unit is necessary to adjust the distance between the cages in a short time in the deceleration period, thereby leading to increased cost in equipment.